The large Volvo® and similar diesel engines used in road tractors (herein referred to simply as a diesel engine) utilize an engine brake to aid in slowing the vehicle. The engine brake in modern diesel engines utilizes a brake rocker arm with additional cam shaft lobes to selectively open and close the exhaust valves. The brake rocker arm interacts with the exhaust valve rocker arm via a pump piston and power piston to operate the engine brake. During normal operation, the pump piston and power piston are provided with low pressure engine oil and are thus in a collapsed state. To effect operation of the engine brake, an oil control valve increases the pressure of oil provided to the pump piston and power piston such that the brake rocker arm pressing on the pump piston causes expansion of the power piston and thus causes the exhaust valves to open.
One problem with the present engine brake system is that the various parts associated with the power piston are not captively held inside of the exhaust rocker arm and can fall out of the rocker arm while servicing the engine. A variety of types of service to the head of the engine such as removal of the head, service to the valve train, or service or replacement of the fuel injectors or injector seals would allow the power piston to fall out of the exhaust rocker arm. This would result in lost time to reassemble the power piston and may result in lost or damaged parts.
The factory service procedures for these engines instruct the service technician to place a rubber band around the power piston to keep it from falling out of the exhaust rocker arm. The rubber band, however, is difficult for the technician to use, does not hold up well to the oil and other chemicals present in the engine, and may damage the engine if the technician forgets to remove the rubber band after servicing the engine. If used, the rubber band may weaken and break due to the oils and solvents used in service and operation of the engine. This may cause the power piston and associated parts to fall out of the rocker arm and be lost or damaged, in addition to increasing the time to service the engine. If the technician forgets to remove the rubber band after performing the desired engine service, the rubber band may interfere with the operation of the engine and may clog oil passages or other parts of the engine, causing damage to the engine. This may occur as the rubber band collects oil and becomes more difficult to see while service is being performed.
There is a need for a tool which is suitable for retaining the power piston in large diesel engines while servicing these engines. There is a need for a tool which is easy to use and reliably prevents the power piston from falling out of the exhaust valve. There is also a need for a tool which is readily visible and which is not easily left in the engine after completing the engine service.